Smoke grenade filling containing encapsulated oil and pyrotechnic materials



United States Patent 3,323,958 SMOKE GRENADE FHLLING CONTAININGENCAPSULATED OIL AND PYROTECHNIC MATERIALS Mitchell Penn and JuliusMiller, Baltimore, Md., assignors to the United States of America asrepresented by the Secretary of the Army No Drawing. Filed Aug. 3, 1965,Ser. No. 477,041 7 Claims. (Cl. 149-11) The invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes, without the payment to us of any royalty there- This inventionrelates to a novel smoke-generatingcomposition and more particularly toan improved mixture which may be used as a filling for smoke grenadesand and other smoke-producing munitions.

Various methods for generating screening and signaling smokes have aserious drawback in that dense clouds or smoke are more or less toxic.In addition, highly corrosive acid fumes render such smoke producers asoleum, sulfur trioxide and chlorosulfonic acid less desirable for use onconcealing friendly troops and their military equipment.

A more suitable source of smoke, one which provides a substantiallynontoxic white smoke, is the liquid hydrocarbon called fog oil, which isvaporized in various generators and the vapor condenses immediately inthe air as minute oil droplets. Various smoke generators have beendevised to evaporate the oil, but they are handicapped by complexity ofdesign and by weight. An mportant consideration in designing the smokegenerating equipment is the requirement for separate compartments forthe oil and for the pyrotechnic which supplies the heat forvaporization. Thus, previous approaches for generating oil smoke or fogwere directed toward oil-vaporizing equipment in which liquid oil wasfed into a vaporizing region heated externally by a pyrotechniccomposition.

The present invention is based on a novel composition which is capableof generating oil smoke in a simplified manner, said smoke being moreeflectively utilized by troops in the field for screening or signalingpurposes, The present composition is capable of autocombustion, nate aninclosed oil as a screening fog. The composition of this invention maybe conveniently employed as a filling for conventional smoke grenades,smoke pots, shells, motor rounds or bombs, thus obviating the previousrequirement for maintaining a separate heat source to vaporize the oil.

It is therefore an object of the invention to provide a novel smokeagent and a heat source in a homogeneous composition for generatingsmoke more conveniently.

Another object of the invention is to provide an oilbearing ingredientin an intimate mixture with one or more pyrotechnic ingredients toproduce an oil fog.

A further object of the invention is to provide the combination of anovel filling in a conventional chemical munition whereby oil smoke maybe generated by ignition of said filling.

Other objects and advantages will become apparent from the followingdetailed description of the invention.

According to the invention, an oil-bearing smoke agent is intimatelymixed with pyrotechnic ingredients to form a solid mixture which can bereadily ignited to generate oil smoke. The smoke agent consists of solidparticles containing therein oil as the central nucleus and surroundinthe oil is an encapsulating wall which is substantially impermeable tothe oil. The encapsulating wall may be formed of a gelled colloid, i.e.gelatin or calcium algi- 3,323,958 Patented June 6, 1967 nate, or it maybe formed of an artificial polymer as a dense oil-impermeable capsule.The solid particles may be of microscopic size measurable in microns, orthey may be of macroscopic droplets visible to the unaided eye. Thus,encapsulated oil, as an apparently dry entity, may form intimatemixtures with solid pyrotechnic ingredients, and said mixtures areconsiderably easier to handle and load into various munitions.

The encapsulation of oil according to the invention provides a densecoating around each droplet of oil; the inclosed oil is unreactivetoward the coating and is retained indefinitely without loss due toleakage or chemical action. Thus, a fluid oil which is encapsulated maybe handled and stored in the manner of any solid material. The fluid oilmay constitute as much as of volume of the particle, yet the oilcontained therein is protected from contact with the surroundingenvironment. The encapsulating material is preferably formed by methodsthat assure a continuous, uniformly thick capsular wall. Gellablesubstances, such a gelatin or calcium alginate, may be effectivelydeposited as a colloidal gel which remains impermeable to the passage ofoil. A solid polymer may also be formed into a capsular material bypolymerization reactions that solidify a liquid monomer around each oildroplet. Monomers which may be mentioned in connection with polymerformation are methacrylates, methylmethacrylates and vinyl acetate.

Processes for encapsulating oil are well known in the art and varioussuitable reactions are provided to form a solid coating on oil droplets.Oil-containing capsules may be formed by methods disclosed in US Patent2,969,330, 2,969,331 and Re. 24,899. Other prior art practices providespray drying for convenient preparation of encapsulated oil in asubstantially dry form.

The oil which is utilized for smoke formation and which is encapsulatedin accordance wtih the teachings of this invention is a petroleumhydrocarbon with a high flash point and high ignition temperature inorder to resist burning. Oil which is suitable for this purpose isessentially a lubricant base stock, one which is preferably deasphaltedand dewaxed. Lubricant oil fractions can be vaporized by a burningpyrotechnic, and the vapor is rapidly condensed on hitting the air.

Previous use of oil in smoke generators was limited to very specificfractions based on their liquid flow characteristics and being free ofconstituents that would shorten the life of the generator. Smokegenerators have utilized low viscosity oils, referred to as SmokeGenerator Fog Oils, SGF #1 and SGF #2 (MILF1207OA) based on viscosityand pour point at specified temperatures. The present use of oil in theform of oil-bearing particles is no longer dependent on liquid fiowproperties of the oil. Consequently, the present encapsulation of fogoil extends the effective range of hydrocarbons which may be utilized inproducing a smoke screen. Ordinary motor oil may be encapsulated andused as a smoke agent, as well as crude oil and other hydrocarbons. Oilswith flash points of about 300 or more and ignition temperatures over380 F. may now form smoke agents for the present invention.

In a particular application of encapsulated oil, a lubricant oilidentified as 500 pale oil was encapsulated with a high quality pigskingelatin. An aqueous solution containing 20 grams of gelatin in grams ofwater was stirred with 80 grams of the oil at 55 C. to form an emulsion.A 20% solution of sodium sulphate was then added slowly keeping thetemperature at about 55 C. until a definite cloudiness was observed inthe mixture. At this point gelatin molecules were deposited around eachoil droplet. The mixture was then cooled rapidly by pouring it into alarge quantity of 10% sodium sulphate solution at room temperaturecausing the gelatin 3 to solidify rapidly. The solid material was thenseparated, washed and dried. I

The following examples are illustrative of suitable" solid mixturescontaining encapsulated oil:

In the examples given above, the encapsulated oil is combined with acombustible material (sucrose), an oxidant (potassium chlorate) and astabilizer that controls the burning rate (magnesium'carbonate). Theburning time can be regulated by adjusting the proportions of oxidantand combustible materials. The above mixtures contain oxygen forsupporting combustionand burn progressively, the burning being a surfacephen'OmenOnLOt'her ingredients may be substituted to vary thepyrotechnic properties, as known by these skilled in the art. The

I utilized in a solid filling for smoke grenades and other amount ofencapsulated oil which may be used with ipyrotechnic mixtures may varywithin certain limits,

suitably between -50 percent by weight.

Mixtures of encapsulated oil and pyroteehnic'rnay be. used as a fillingin various burning-type munitions; for example, smoke grenades smokepots, candles or vfioating boxes in naval use. When the pyrotechnic'isignited, the heat released is sufficient to volatilize the encapsulatedoil, which then condenses outside the munition to form portable typesmoke munitions for the generation of nontoxic smoke screen.

Since many modifications and variations may be made from the foregoing,we intend to be limited only as inclicated by the following claims.

We claim:

1. A'smoke-generating composition comprising:

an encapsulated oil, gelled colloid forming the capsular material ofsaid oil, pyrotechnic consisting'of a fuel material, oxidant andstabilizer for vaporizing said oil,

said encapsulated oil, and said pyrotechnic forming a homogeneous solidmixture.

2. A smoke-generating composition accordingto claim l'wherein saidhydrocarbon consists of a lubricant motor oil- I 3. A smoke-generatingcomposition according to claim 1 wherein said capsular material consistsof an artificial polymer.

4. A smoke-generating composition according to claim '1 wherein saidcolloid is composed of gelatin.

5. A smoke-generating composition according to claim v ;1 wherein saidcolloid is composed of calcium alginate.

. chlorate and magnesium carbonate.-

7. A smoke-generatingcomposition according to claim 1 wherein saidencapsulated oilis present in said compo smoke. The entire processdepends upon a high tempera- 3,117,521 3,143,446 8/1964 Berman s l49-2BENJAMIN R. PADGETT, Primary Examil elx,

1/1964 Reaves 102-'65 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3 ,323;9S8" un 6, 1967 Mitchell Penn et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as show below:

Column l, line l6, cancel'nate an inclosed oil as a screening fog. andinsert the heat released being sufficient 1E0 vaporlze and disseminatean inclosed oil as a screening Signed and sealed this 29th day of July1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr. Attesting Officer Commissioner of Patents

1. SMOKE-GENERATING COMPOSITION COMPRISING: AN ENCAPSULATED OIL, AGELLED COLLOID FORMING THE CAPSULAR MATERIAL OF SAID OIL, A PYROTECHNICCONSISTING OF A FUEL MATERIAL, OXIDANT AND STABILIZER FOR VAPORIZINGSAID OIL, SAID ENCAPSULATED OIL AND SAID PYROTECHNIC FORMING AHOMOGENEOUS SOLID MIXTURE.